Certain popular window styles are designed to accommodate inward tilting of a lower sash member about a pivot axis adjacent to a lower edge thereof. This allows for ventilation without raising the sash and also simplifies access to the outer surfaces of the glass pane(s) for cleaning etc. The tiltable sashes are provided with latch mechanisms, sometimes referred to as tilt latches, at opposite sides of the top sash rail, to provide releasable locking engagement of the sash rail with opposite sides of the window frame. The tilt latches include sliding bolts that are spring actuated toward their locking positions while providing for manual release for tilting of the sash.
A representative form of tilt latch of the above-described type is illustrated and described in the Schultz U.S. Pat. No. 5,139,291. The mechanism of the Schultz patent is made up of a plastic housing in which a plastic latch bolt is received for sliding movement between extended (locking) and retracted (release) positions. A metal actuating spring is provided, positioned between elements of the latch bolt and elements of the housing, to bias the latch bolt toward its extended or locking position while permitting temporary manual retraction to a release position in order to be able to pivot the sash to an open position.
While the latch mechanism of the Schultz patent can function satisfactorily, the use of a metal actuating spring creates unfavorable cost issues relating to the cost of the spring and the assembly cost involved in incorporating the spring into the assembled mechanism. Efforts have been made in the past to reduce this cost factor by combining the latch bolt and the actuating spring as a single part of molded plastic, with a plastic spring integrally molded as an extension of the latch bolt. Examples of such efforts are the Harbom et al U.S. Pat. No. 5,121,951 and the Szapucki et al US patent RE37,916, each of which illustrates a form of actuating spring, molded of plastic material, integrally with the latch bolt. Although the proposals of these patents were published many years ago (more than ten years in the case of RE37,916 and more than twenty years in the case of U.S. Pat. No. 5,121,951), no such latch bolt mechanisms are commercially available at this time, notwithstanding the significant manufacturing and assembly cost savings that could be realized by integrally molding the spring with the latch bolt. With previous designs the integrally molded spring elements were not suitable to the task required, and the integrated construction, notwithstanding its many advantages in the production and assembly phases, has not achieved commercial success.